Security Vulnerability in Solaris SSH May Allow Unauthorized Access to X11 Sessions

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A Security Vulnerability in Solaris SSH may allow Unauthorized Access to X11 Sessions

1. Impact

A security vulnerability related to X11 forwarding within the SSH product shipped with Solaris may allow a local unprivileged user to gain unauthorized access to another user's X11 session. This may allow execution of code with the privileges of that user or may result in the disclosure of sensitive data related to the user's session.

This issue is also referenced in the following document:

2. Contributing Factors

This issue can occur in the following releases:

SPARC Platform

• Solaris 9 without patch 114356-14
• Solaris 10 without patch 126133-03
  

x86 Platform

• Solaris 9 without patch 114357-13
• Solaris 10 without patch 126134-03
  

Note:  SSH is not shipped with Solaris 8 and therefore is not impacted by this issue.

This issue only affects systems which are configured to run the SSH service. The following can be used to determine if the sshd(1M) daemon is running on a host:
This issue only affects SSH sessions which have X11 forwarding enabled. By default users are allowed to enable this facility for any new sessions (see sshd(1)). To determine whether the X11 forwarding setting has been changed from the default, the sshd_config(4) file can
be examined, for example:

3. Symptoms

There are no predictable symptoms that would indicate the described vulnerability has been exploited.

4. Workaround

To workaround this issue, X11 forwarding can be disabled for individual SSH sessions by running the ssh(1) as follows when those sessions are initiated:
OR   
Alternatively, the sshd_config(4) file on a host can be modified to disable X11 forwarding for all incoming SSH connections to that host, by changing the following line in "/etc/ssh/sshd_config" (or adding it if not already present) from:

to
       
and then restarting ssh:

For Solaris 9:
For Solaris 10:

5. Resolution

This issue is addressed in the following releases:

SPARC Platform

• Solaris 9 with patch 114356-14 or later
  
• Solaris 10 with patch 126133-03 or later

x86 Platform

• Solaris 9 with patch 114357-13 or later
  
• Solaris 10 with patch 126134-03 or later
  

Note: The above patches have introduced a regression for systems that have only IPv4 interfaces configured. Please see Sun Alert 240906 for further information.

For more information on Security Sun Alerts, see Technical Instruction ID 213557.

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Modification History

23-May-2008: Updated Contributing Factors and Resolution sections
02-Jul-2008: Updated Contributing Factors and Resolution sections; now Resolved
20-Aug-2008: Updated Resolution section

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